Top-quark pole mass

TL;DR

The paper addresses whether the top-quark pole mass can be defined unambiguously in QCD. It presents a general S-matrix argument and a detailed infrared renormalon analysis showing that the pole mass inevitably carries an ambiguity of order Lambda_QCD, even for a rapidly decaying top quark. The width of the top quark does not cure this nonperturbative ambiguity, and the authors advocate using a short-distance MSbar mass instead. They provide two-loop relations connecting pole and MSbar masses and illustrate with a realistic top-quark mass, highlighting the practical impact for precision mass determinations.

Abstract

The top quark decays more quickly than the strong-interaction time scale, $\lqcd^{-1}$, and might be expected to escape the effects of nonperturbative QCD. Nevertheless, the top-quark pole mass, like the mass of a stable heavy quark, is ambiguous by an amount proportional to $\lqcd$.

Figures (4)

• Figure 1: A scattering amplitude factorizes when an internal propagator is near its pole. The external lines represent color-singlet asymptotic states.
• Figure 2: The production and decay of a top quark in (a) perturbation theory, and (b) nonperturbatively.
• Figure 3: Diagrams contributing to the top-quark self-energy at leading order in $\alpha_s$ and $\alpha_W$. Fig. (a$^\prime$) replaces Fig. (a) when summing to all orders in $\beta_0\alpha_s$.
• Figure 4: Diagrams contributing to the top-quark self energy at leading order in $\alpha_s$, but to all orders in $\alpha_W$. Fig. (a$^\prime$) replaces Fig. (a) when summing to all orders in $\beta_0\alpha_s$.